Evaluation of cognitive functions in euthymic bipolar patients using mono- and multi- drug treatments

Objective: Some studies on patients suffering from bipolar disorder show that in active and remission periods of the disorder there are cognitive insufficiencies (1,2,3). The causes of cognitive insuffuciencies in bipolar disorder is not understood yet. We anticipate that multi-drug usage has more adverse effects on cognitive functions than mono- drug usage and our aim in this study was to investigate effects of drugs used in treatment of bipolar disorder on cognitive functions. In this study we evaluated the cognitive functions of bipolar patients who were in their euthymic period taking mono- and multi-drug regimens and compared them with a healthy control group.

Methods: Eighty bipolar I and II patients diagnosed based on the DSM-IV criteria and 80 healthy controls were included in the study and two groups matched according to age, sex, and education aspects. The patients and controls gave written informed consent to participate in the study. The necessary approval and ethic committee reviews and permits were obtained prior to the study. The patients were evaluated using a psychiatric interview, the Young Mania Scale and the Hamilton Depression Rating Scale. A large neurocognitive battery (Wechsler Memory Scale-Revised, Stroop,Verbal Memory Processes Scale) was used for neurocognitive assessment.

Results: In most cognitive tests the results of the patient group were worse than the control group. The Verbal Memory Processes Scale-learning scores and long term memory scores were higher in the patients on a mono-drug regimen. All other tests did not show significant differences.

Conclusions: Our study showed that the cognitive function of bipolar patients had deficiencies not only in active periods of bipolar disorder but also in remission periods, like previous studies (4,5,6). The Verbal Memory Processes Scale learning scores and long term memory scores showed better results in patients using a mono-drug compared to the ones on a multi-drug regimen. Other tests did not show significant differences. Future studies with larger number of patients may show different results. Also other studies to investigate the effects of each drug group on cognitive functions in bipolar patients are needed.